Transcript Fibrinogen

Afibrinogenemia
• Prevalence approx 1:1,000,000
• Recessive inheritance
– Most reported cases from consanguineous parents
– Parents typically have asymptomatic hypofibrinogenemia
• Genetically heterogeneous (>30 mutations)
• May be due to failure of synthesis, intracellular transport or
secretion of fibrinogen
• Moderate to severe bleeding (typically less than in severe
hemophilia)
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Death from intracranial bleeding in childhood may occur
GI and other mucosal hemorrhage
Menorrhagia
Placental abruption
• Treat with purified fibrinogen concentrate or cryoprecipitate for
bleeding, during pregnancy
Inherited dysfibrinogenemia
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Prevalance uncertain (most cases asymptomatic)
Usually exhibits dominant inheritance
Most cases due to missense mutations
Mutations may affect fibrin polymerization,
fibrinopeptide cleavage, or fibrin stabilization by
FXIIIa
• Variable clinical manifestations (mutationdependent):
– Over 50% asymptomatic
– Approx 25% with bleeding tendency (mild to severe)
– 20% have a thrombotic tendency (arterial, venous, or both)
• Decreased thrombin-binding (antithrombin effect) of fibrin?
• Altered fibrin clot structure?
Acquired dysfibrinogenemia
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Usually associated with liver disease
– Cirrhosis
– Acute hepatitis
– Hepatoma
Fibrinogen has higher than normal sialic acid content
Diseased liver has increased levels of sialyltransferase and other
enzymes that control oligosaccharide content
JCI 1978;61:535
Diagnosis of dysfibrinogenemia
• Prolonged thrombin & reptilase times
– PT, aPTT may be prolonged
• Disparity (>30%) between fibrinogen
activity and antigen
• Family testing
• Evaluate for liver disease
Arch Pathol Lab Med 2002;126:499
Other acquired abnormalities of fibrin
formation
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High fibrinogen
High levels of FDP
Myeloma proteins (IgM > IgA > IgG)
Autoantibodies
Recessively inherited clotting factor
deficiencies
• Rare
– Exceptions: XI, XII deficiency
• Homozygotes (often consanguineous parents) or
compound heterozygotes
• Heterozygous parents usually asymptomatic
• Quantitative (“type 1”) deficiency: parallel reduction
in antigen and activity
• Qualitative (“type 2”) deficiency: reduced activity
with near-normal antigen
• Genetically heterogeneous
• Complete deficiency of II, X not described (lethal?)
• Mutation usually in gene encoding clotting factor
Exceptions:
Combined V, VIII deficiency
Combined deficiency of vitamin K-dependent factors
Combined deficiency of factors V and VIII
• Levels of affected factors 5-20% of
normal
• Associated with mutations of LMAN-1
(ERGIC-53) or MCFD2, both of which
regulate intracellular trafficking of V
and VIII
Deficiency of multiple vitamin-K
dependent clotting factors
• Levels of II, VII, IX, X, proteins C and S
range from <1% to 30% of normal
• Bleeding symptoms proportional to
degree of deficiency
• Usually associated with missense
mutations in vitamin K epoxide
reductase subunit 1 (VKORC1)
Relative frequencies of recessively
inherited factor deficiencies
Blood 2004; 104:1243
Clinical features of recessively inherited
factor deficiencies
Blood 2004; 104:1243
Patterns of bleeding in recessively
inherited factor deficiency vs hemophilia
Blood 2004; 104:1243
Treatment of rare clotting factor deficiencies
• FFP
• Prothrombin complex concentrate (II, VII, IX, X) or
specific factor concentrate (XIII – others available in
Europe) when appropriate
• Goal is to maintain “minimal hemostatic levels”
• Antifibrinolytic drugs may be helpful in patients with
mucosal hemorrhage
• Routine prophylaxis appropriate for F XIII deficiency
(long half-life, low levels adequate for hemostasis)
• Otherwise treatment appropriate for active bleeding
or pre-procedure
Factor XI
XI
XIa
VIII
IX
IXa
VIIIa
V
Xa
Va
Propagation
Injury
TF
VIIa
Initiation
X
PT
Xa
Thrombin
Fibrinogen
Fibrin
Factor XI deficiency
• Recessively inherited
• Most common in individuals of Ashkenazi
Jewish descent
– 2 common mutations (one nonsense, one
missense)
– Allele frequency as high as 10%, 0.1-0.3%
homozygous
– Most affected patients compound heterozygotes
with low but measurable levels of XI activity
• Long aPTT, normal PT
– XI activity < 10% in most patients with bleeding
tendency
Factor XI deficiency
Clinical features & treatment
• Variable, generally mild bleeding tendency
– Bleeding after trauma & surgery
– Spontaneous bleeding uncommon
– Bleeding risk does not correlate well with XI level
• Treatment: FFP
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15 ml/kg loading, 3-6 ml/kg q 12-24h
Half life of factor >48 hours
Amicar useful after dental extraction, surgery
rVIIa is effective but expensive; thrombotic
complications reported
Factor XIII
• Transglutaminase: forms amide bonds
between lysine and glutamic acid residues
• Heterotetramer (A2B2) in plasma
– A chains made by megakaryocytes and
monocyte/macrophage precursors
– Platelet XIII (50% of total XIII) has only A chains
– B chains (non-catalytic) made in liver
• Proenzyme activated by thrombin
• Crosslinks fibrin
Inherited factor XIII deficiency
• Autosomal recessive, rare
(consanguineous parents)
• Heterozygous woman may have higher
incidence of spontaneous abortion
• Most have absent or defective A
subunit
• F XIII activity < 1%
Inherited factor XIII deficiency
Clinical features & treatment
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Bleeding begins in infancy (umbilical cord)
Poor wound healing
Intracranial hemorrhage
Oligospermia, infertility
Diagnosis:
– Urea solubility test
– Quantitative measurement of XIII activity
– Rule out acquired deficiency due to autoantibody
• F XIII concentrates available (long half life,
can administer every 4-6 weeks as
prophylaxis)
Acquired factor XIII deficiency
• Autoantibody-mediated
– Very rare
• Most patients elderly
• May be drug-induced (isoniazid, other
antibiotics)
• Bleeding may be severe
• Diagnosis:
– Urea solubility
– F XIII activity
– Mixing study?
Factor XII deficiency
• Recessive inheritance, but fairly
common
• Markedly prolonged aPTT
No bleeding tendency
• Deficiency of other contact factors
(HMWK, prekallikrein) less common,
but has similar phenotype
PLATELET DISORDERS
Platelet structure 1
• Membrane glycoproteins
– IIb-IIIa: integrin, cryptic in resting platelet,
after platelet activation binds fibrinogen
and other adhesive proteins, necessary for
aggregation
– Ib-IX-V: binds VWF, necessary for platelet
adhesion at high shear rates
– Ia-IIa: integrin, binds collagen, mediates
adhesion at low shear rates and platelet
spreading (also acts as receptor)
Platelet structure 2
• Membrane receptors
– Thrombin receptors (2): cleaved and
activated by thrombin
– Thromboxane A2 receptor
– ADP receptors (3)
– Epinephrine receptor
– Serotonin receptor
– Cytokine, chemokine receptors
– Fc receptor
Platelet structure 3
• Membrane phospholipids
– Procoagulant lipids (phosphatidyl serine)
sequestered on inner leaflet, transferred to
outer leaflet by “scramblase” enzyme with
platelet activation
– Arachidonic acid cleaved from inner leaflet
by phospholipase, converted to
thromboxane by cyclooxygenase &
thromboxane synthase
Platelet structure 4
• Granules
– Dense granules: small molecules involved
in platelet activation (ATP/ADP, serotonin)
– Alpha granules: fibrinogen, fibronectin,
thrombospondin, P-selectin, plasminogen,
alpha-2 antiplasmin, factor V, PF4, PDGF,
TGF-alpha and beta, ECGF
Bernard-Soulier syndrome
• Pathophysiology:
– Deficiency of platelet membrane glycoprotein Ib-IX (VWF
“receptor”)
– Defective platelet adhesion
• Clinical: Moderate to severe bleeding
• Inheritance: autosomal recessive
• Morphology:
– Giant platelets
– Thrombocytopenia (20-100K)
• Diagnosis:
– No agglutination with ristocetin, decr thrombin response,
responses to other agonists intact
– Morphology
– Decreased GP Ib expression
Bernard-Soulier syndrome
Glanzmann thrombasthenia
• Pathophysiology:
– Deficiency of platelet membrane GPIIb-IIIa
– Absent platelet aggregation with all agonists;
agglutination by ristocetin intact
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Clinical: Moderate to severe bleeding
Inheritance: autosomal recessive
Morphology: normal
Diagnosis:
– Defective platelet aggregation
– Decreased GP IIb-IIIa expression
Gray platelet syndrome
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Pathophysiology: Empty platelet alpha granules
Clinical: Mild bleeding
Inheritance: Autosomal dominant or recessive
Morphology:
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Hypogranular platelets
Giant platelets
Thrombocytopenia (30-100K)
Myelofibrosis in some patients
• Diagnosis
– Variably abnormal platelet aggregation (can be normal)
– Abnormal platelet appearance on blood smear
– Electron microscopy showing absent alpha granules
Gray platelet syndrome
Giant platelet syndromes associated
with MYH9 mutations
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May-Hegglin anomaly
Fechtner syndrome
Sebastian syndrome
Epstein syndrome
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All associated with mutations in the non-muscle
myosin heavy chain gene MYH9
Thrombocytopenia with giant platelets, but mild
bleeding
Autosomal dominant inheritance
No consistent defects of platelet function detectable
in the clinical laboratory
Diagnosis usually based on clinical picture, family
history, examination of blood smear for neutrophil
inclusions
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Giant platelet syndromes associated
with MYH9 mutations
Syndrome
MayHegglin
Fechtner
Sebastian
Epstein
Neutrophil Hereditary Deafness
inclusions nephritis
Yes
No
No
Yes
Yes
Yes
Yes*
No
No
No
Yes
Yes
*Neutrophil inclusions have different structure from those in May-Hegglin
Neutrophil inclusions in May-Hegglin
anomaly
Wiskott-Aldrich syndrome
• Pathophysiology
– Mutation in WASP signaling protein
– Decreased secretion and aggregation with multiple
agonists; defective T-cell function
• Clinical:
– Mild to severe bleeding
– Eczema, immunodeficiency
• Inheritance: X-linked
• Morphology:
– Thrombocytopenia (20-100K)
– Small platelets with few granules
• Diagnosis: Family hx, clinical picture, genetic
testing
Wiskott-Aldrich syndrome
Hermansky Pudlak syndrome
Chédiak-Higashi syndrome
• Pathophysiology:
– Platelet dense granule deficiency: decreased aggregation &
secretion with multiple agonists
– Defective pigmentation
– Defective lysosomal function in other cells
• Clinical:
– Mild to moderate bleeding
– Oculocutaneous albinism (HPS)
– Lysosomal storage disorder with ceroid deposition, lung & GI
disease (HPS)
– Immunodeficiency, lymphomas (CHS)
• Inheritance: autosomal recessive
• Morphology
– Reduced dense granules
– Abnormal neutrophil granules (CHS)
• Diagnosis: clinical picture, neutrophil inclusions (CHS), genetic
testing
HPS, with oculocutaneous
albinism
Chédiak-Higashi,
showing neutrophil
inclusions
Hermansky-Pudlak syndrome
Br J Haematol 2007;138:671
Disaggregation after primary aggregation with ADP
Dense granule deficiency
Control platelet
Platelet type von Willebrand disease
• Pathophysiology: Gain of function mutation in GP
Ib, with enhanced binding to VWF and clearance of
largest multimers from blood
• Clinical: Mild to moderate bleeding
• Inheritance: Autosomal dominant
• Morphology: Normal, but platelet count often low
• Diagnosis: Variably low VWF antigen,
disproportionately low ristocetin cofactor activity,
loss of largest VWF multimers on electrophoresis,
enhanced platelet agglutination by low dose
ristocetin (indistinguishable from type 2B VWD)
• Can distinguish from 2B VWD by mixing studies with
normal/pt platelets and plasma and low dose
ristocetin, or by genetic testing
Treatment of patients with platelet disorders
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Platelet transfusions
DDAVP
Antifibrinolytic drugs (Amicar)
rVIIa?
• Treatment decisions must be
individualized
VASCULAR DISORDERS
Hereditary Hemorrhagic Telangiectasia
• Autosomal dominant inheritance
• Mutation in endoglin gene that controls
vascular remodeling
– Molecular diagnosis possible
• Multiple small AVMs in skin, mouth, GI
tract, lungs
Endoglin and vascular remodeling
J Thromb Haemost 2010;8:1447
Hereditary hemorrhagic telangiectasia
J Thromb Haemost 2010;8:1447
Hereditary Hemorrhagic Telangiectasia
Clinical features
• Epistaxis, GI bleeding – may be severe
– Severe iron deficiency common
• Pulmonary or CNS bleeding often fatal
• Gradual increase in bleeding risk with
age
• AVMs enlarge during pregnancy
• Risk of brain abscess
• Hypoxemia from pulmonary HTN and
R→L shunting in lung
Hereditary Hemorrhagic Telangiectasia
Treatment
• No consistently effective method for
preventing bleeding
• Aggressive iron replacement
• Antibiotic prophylaxis for dental work
etc
• Screen for CNS lesions → consider
surgical intervention
Ehlers-Danlos syndrome
• Defective collagen structure
– Mutations in genes for various types of collagen
• 9 variants
– Type IV (mutation in type III collagen gene) most
likely to cause bleeding
• Bleeding due to weakening of vessel wall →
vessel rupture
• Conventional tests of hemostatic integrity
normal
Ehlers-Danlos syndrome
• Thin, weak skin with poor healing
– “Cigarette paper” scars
• Bruising
• Hypermobile joints
– Spontaneous joint dislocation
• Median survival 48 years in type IV EDS
– Death from rupture of large vessels or
colon perforation